A technique is known by which, when a battery module with a plurality of electric cells arranged and connected to each other is electrically connected to another electrical device that is arranged on a side of the battery module, a connection bus bar is arranged to span an electrode at an end portion of the battery module and a connecting portion of the electrical device (e.g. Patent Document 1 JP2004-95381A). In a specific example, in view of different height positions of the electrode of the battery module and the connecting portion of the electrical device (e.g. the connecting portion of the electrical device is located at a higher position than the electrode of the battery module), a means has been proposed in which an L-shaped welding plate with a flat welding face is later attached to a leading end of the connection bus bar by means of ultrasonic welding or the like, and a base end of the connection bus bar is fastened and fixed to the connecting portion of the electrical device using a fastening member, and meanwhile, the welding face of the welding plate is placed on the electrode of the battery module and is fixed by means of laser welding.